The present invention relates to a roll press, preferably for the treatment of a traveling web, for instance a web of paper. The roll press comprises two press units, for example press rolls, the main axes of which lie in a pressing plane and form with each other a press nip through which the web travels. The roll press can also comprise three press units which form two press nips, or four press units which form three press nips.
The invention proceeds from a roll press having the following features. It is a roll press for the treatment of a traveling web of paper having two press units which may be in the form of press rolls. Each press unit, hereafter called a press roll, has a respective axis. The axes together lie in a press plane. The press rolls are so placed as to define a first press nip between them. One of the two press rolls includes a stationary support member that supports a traveling or circulating press element around the support member and that supports an internal pressing device for radially outwardly biasing the traveling or circulating press element toward the web and the other press roll. There are respective bearing brackets at each end of each of the press rolls. The bearing brackets at each end of the rolls are connected to each other by detachable tension bars which transmit the pressing force between the bearing brackets at the respective roll end. One set of the bearing brackets for one of the press rolls are rigidly supported on a machine frame or foundation and bear or support the weight of the other press roll. As prior art, referencee is had to WO 92/17641 published after the priority date claimed.
The "main axis" of a press unit can, for instance, be the axis of rotation of a press-roll jacket or the longitudinal axis of the stationary support member of, for instance, a shoe-press unit (in the latter case, the axis of rotation can be arranged eccentrically relative to the main axis).
The "rotating press element" can be a metallic press-roll jacket which is rotatable around a stationary support member and is displaceable radially relative to it, or a traveling or circulating press belt or tubular traveling or circulating press jacket in the case of a shoe press unit.
The "internal pressing device" can be either a pressure chamber in the shape of a half ring or a row of radially movable support elements, or else an elongated radially movable press shoe.
The "one press unit", the bearing brackets of which are rigidly supported, is arranged on a frame, foundation or the like or is fastened (by means of its brackets) suspended from a (for instance, vertical or horizontal) support. The "other press unit" can be arranged above, to the side of, or below the rigidly supported press unit and its weight is borne by the bearing brackets of the rigidly supported press unit. The expression "rigidly supported" includes the bipartite bearing-bracket construction with axial guide elements in accordance, for instance, with Federal Republic of Germany Utility Model 92 04 405.0.
One essential feature of the roll press from which the present invention proceeds is that the bearing brackets are coupled to each other in pairs by means of detachable tension bars. These tension bars are the sole element for transmitting the pressing force from bearing bracket to bearing bracket. Thus, the machine frames of the roll press need be dimensioned only for the weight of the press units themselves, and not for the transmission of the pressing force. It is also important that the tension bars are easily detachable so that the tension bars, while in an unloaded condition thereby exerting zero pressing force, are preferably pretensioned to at most a fraction of the maximum pressing force.
Furthermore, these tension bars are in a certain sense movable or flexible so that the bearing brackets of the "other press unit" are movable parallel to the pressing plane relative to the bearing brackets of the rigidly supported press unit. This is in contradiction to the manner of construction in accordance with U.S. Pat. No. 3,921,514. In that patent, instead of easily detachable tension bars, bolted connections are provided which clamp the bearing brackets together. Thus, these bolted connections must be strongly prestressed already in the unloaded condition of the roll press. Such bolted connections are extremely bulky and expensive in highly loaded roll presses. Thus mounting and loosening of the bearing brackets can be effected only at enormous expense. In this connection, it must be borne in mind that such roll presses are preferably used in paper manufacturing machines, the width of which may in the extreme case be up to 10 m. In particular, many roll presses are developed as shoe presses in which the linear force prevailing in the press nip may reach an order of magnitude of 1000 kN/m. To complicate matters, in many cases an endless felt belt (serving for the removing of water from the web of paper) must pass through the press nip and such a felt belt must be replaced at certain time intervals by a new felt belt. Similarly, in the case of shoe presses, the rotating flexible (for instance, tubular) press element must be replaced from time to time. Due to the use of the easily detachable tension bars, this work can be carried out within a relatively short time, so that the roll press is quickly ready to operate again.
One disadvantage of this proposed construction is, however, that an exact positioning of the two bearing brackets relative to each other is not possible, even though guide cheeks are provided on the machine frame. In other words, there is the danger that the main axis of the "other" press unit having the movable bearing brackets does not lie (at least at times) precisely in the pressing plane. This has the result that the web is treated in a nonuniform manner over its width, and/or that the roll jackets become unevenly worn.